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نویں جماعت · طبیعیات · 6 سوالات

نام: ____________________ تاریخ: ____________

Heat travels through a solid mainly by:
- A Convection
- B Conduction
- C Radiation
- D Evaporation
Heat reaches the Earth from the Sun by:
- A Radiation
- B Reflection only
- C Convection
- D Conduction
Convection takes place in:
- A Fluids
- B Solids only
- C A vacuum
- D Metals only
Which of these is a good conductor of heat?
- A Air
- B Wood
- C Copper
- D Plastic
A vacuum flask keeps liquids hot mainly because it reduces:
- A Conduction, convection and radiation
- B Only radiation
- C Only conduction
- D Only the liquid's mass
Which colour of surface is the best absorber of heat radiation?
- A Dull black
- B Silver
- C Shiny yellow
- D White

جوابی کلید

1. B, 2. A, 3. A, 4. C, 5. A, 6. A

In solids heat is passed from particle to particle by conduction.
Radiation does not need a medium, so it can cross empty space.
Convection needs the bulk movement of a liquid or gas.
Metals such as copper conduct heat well. Wood, plastic and air are poor conductors.
The vacuum stops conduction and convection, and the shiny walls reduce radiation.
Dull black surfaces absorb and emit radiation best.